Ok I have an six that has the factory radio and tape deck, with the 6 disc c in the ext cab area. When I turn on the radio or tape I have to turn it all the way up and can barely hear it. If I play the CD player it is normal volume as always, maybe like 3 or 4 bars of the 15 on the display.

I'd say something isn't plugged in all the way. Like if you have the 1.8mm cable for an ipod or something and it gets partially pulled out and you can barely hear the music. I would check wiring. If it looks normal go ahead and unplug stuff and plug it back in. Sometimes that little bit of removing and installing a plug can make a bad connection come back to life. simple, easy and free fix if it does fix it lol.